After 1500 games, you still don't have a good idea what your ROI is. You can say some things about what your ROI probably isn't, but you haven't pinned down your win rate. A rough 95% confidence interval for your expected ROI after n 9-player STTs is your observed ROI +- 310%/squareroot(n). If n=1500, that is about your observed ROI +- 8%, which means it's not a big surprise to run up to 8% above or 8% below your true ROI in 1500 tournaments.
The all-in luck adjustment removes a little more than half of the variance in turbo SNGs (and more like 70% in super turbos). This means in your next 500 tournaments, it isn't a big surprise to see up to about a 10% ROI difference between your red line and green line, or between your red line and your true ROI.
You are right on the border of the +- 10% interval, but you are looking backwards. There are many opportunities to observe streaks of good luck or bad when you look backwards, which makes them much less rare. If you can predict that you will toss a coin and get heads on the next 7 tosses, that would be remarkable, and it would be evidence that you can control the coin toss or the coin isn't fair. However, if you toss a coin 100 times, it's pretty likely that at some point, you can look backwards and say there was a streak of 7 heads. It's even more common if you weren't looking for only heads, and would also point out if you get a streak of 7 tails in a row, as in the other recent thread where someone points out that he ran ahead of expectation for a few hundred SNGs. In order for a past streak to be remarkable, it shouldn't be something that happens 1 time in 20 when you look forward, it might need to be 1 in 1000, or even more extreme if you play for a long time.
After a streak of bad luck, don't assume the cards owe you anything. Cards have no memory, and it's quite possible to drop another 50 buy-ins. If your play is solid and the games are good, you will pull out eventually, but don't count on snapping back quickly, even though when you look backwards you will sometimes see periods of good luck after bad streaks. You can see those because when you have bad luck following bad, you simply combine the two into one bigger streak of bad luck.